The use of synthetic cutting fluid compositions has grown rapidly. The oil-free compositions are designed to impart lubricity at high temperatures, inhibit rust, reduce surface tension, produce low foam and be compatible with concentrated electrolyte solutions for hard water.
Examples of synthetic metal working fluid compositions which may be both oil and water soluble are those formed from conventional non-ionic surfactants which consist of a hydrophobe which has been polyoxyethylated. Such non-ionic surfactants have been provided with a phosphate radical which improves several of the sought for characteristics including increasing the hydrophilic characteristic of such surfactants. Examples of such metal working fluids are the ANTARA.RTM. lubricant compositions which are sold by the GAF Corporation. These metal working fluid compositions are based on aliphatic and aromatic hydrophobic moieties which are further alkoxylated and phosphated.
The present invention provides a particularly suitable synthetic aqueous based metal working fluid which is comprised of phosphated polyethoxylated (2-10 EO) n butane 1,4 diols which are completely hydrophilic in nature. They do not contain any hydrophobic moiety. The particularly novel aspect of the present invention resides in phosphoric acid esters of the condensation products of one mole of butane-1,4-diols with from 2 to 10 moles of ethylene oxide. These esters are useful in a variety of applications where synthetic aqueous based metal working fluids are suited. Such uses are as lubricating additives, corrosion inhibitors, hydraulic fluids, flame retardant additives, plasticizers and the like. The phosphate esters of the present invention may be represented as follows: ##STR1## wherein X is a member selected from the group consisting of H and polyoxyethylbutanol having the general formula: ##STR2## such that the compound can be either a mono-, di- or tri-ester of phosphoric or polyphosphoric acid, or mixtures of the three, m and n are positive integers of 1 or higher. In the case where m and n are greater than 1, their values are similar to the degree of polymerization occuring in polyphosphoric acid; q and p are positive integers the total of which is from 2 to 10 and wherein z is also an integer having a value of 1 or higher.
An examination of the general formula set forth above discloses a straight chain molecule which contains no branched chains. The component moieties of the compound are individually hydrophilic and in combination remain hydrophilic. This is believed to particularly distinguish the compounds of the present invention from those found in the metal working fluids generally available which are based on combinations of hydrophobic and hydrophilic moieties. The straight chain nature of the present compounds indicates a further characteristic that is particularly desirable that of being biodegradable. The compounds of the present invention may be further modified by forming ammonium, substituted ammonium, alkali metal or alkaline earth metal salts thereof.
The preparative methods for synthesizing the rather complex compounds and mixtures thereof of the invention follow well known synthetic procedures. The ethyoxylation is carried out by adding a pre-determined number of moles of ethylene oxide to the terminal hydroxyl groups of the butanediol. It is understood that this addition results in a well known random distribution of oxyethylene groups on either side of the butanediol moiety. The phosphation is also carried out by well known methods. The phosphating agent preferred in the present invention is polyphosphoric acid although P.sub.2 O.sub.5 may also be used. The choice between the two phosphating agents depends upon whether a proponderance of diester or monoester is preferred. Polyphosphoric acid produces more monoester while P.sub.2 O.sub.5 produces more diester.